Mobile Computing Chapter 8: Mobile Network Layermultinet.ivyro.net/recruit/lecture/1-2/mbc-8.pdf · 2008. 10. 7. · Mobile IP Design Goals A mobile node must be able to communicate

The Graduate School of Information Technology and TelecommunicatThe Graduate School of Information Technology and Telecommunications, INHA Universityions, INHA Universityhttp://http://multinet.inha.ac.krmultinet.inha.ac.kr

Multimedia Network Lab.Multimedia Network Lab.

Mobile Computing

Chapter 8: Mobile Network Layer

Prof. Sang-Jo Yoo

2The Graduate School of Information Technology and TelecommunicatThe Graduate School of Information Technology and Telecommunications, INHA Universityions, INHA University

http://multinet.inha.ac.kr Multimedia Network LabMultimedia Network Lab..

ContentsMobile IP overview

Agent discovery

Registration

Tunneling

DHCP

Mobile IP multicasting



Motivation for Mobile IPRouting

based on IP destination address, network prefix (e.g. 129.13.42)determines physical subnetTo avoid an explosion of routing tables, only prefixes are stored aandfurther optimizations are applied.change of physical subnet implies change of IP address to have atopological correct address (standard IP) or needs special entries in the routing tables

Specific routes to end-systems?change of all routing table entries to forward packets to the right destinationdoes not scale with the number of mobile hosts and frequent changes in the location, security problems



Motivation for Mobile IPChanging the IP-address?

adjust the host IP address depending on the current locationAssigning a new IP address (DHCP)

Problem: nobody knows about this new address.Almost impossible to find a mobile system, DNS updates take to long timeTCP connections break, security problems

TCP connection = {source IP, source port, destination IP, destination port}TCP connection cannot survive any address change.



Requirements to Mobile IP

TransparencyMobility should remain ‘invisible’ for many higher layer protocols and applicationsFor TCP, mobile computer must keep its IP address.

Compatibilitysupport of the same layer 2 protocols as IPno changes to current end-systems and routers requiredmobile end-systems can communicate with fixed systems

SecurityThe minimum requirement: all the messages related to the management of Mobile IP are authenticated.

Efficiency and scalabilityOnly little additional messages to the mobile system required (connection typically via a low bandwidth radio link)



TerminologyMobile Node (MN)

system (node) that can change the point of connection to the network without changing its IP address

Home Agent (HA)system in the home network of the MN, typically a routerregisters the location of the MN, tunnels IP datagrams to the COA

Foreign Agent (FA)system in the current foreign network of the MN, typically a routerforwards the tunneled datagrams to the MN, typically also the default router for the MN

Care-of Address (COA)address of the current tunnel end-point for the MN (at FA or MN)actual location of the MN from an IP point of view

Correspondent Node (CN)communication partner



TerminologyCare-of Address (COA)

Foreign agent COAThe COA could be located at the FA (IP address of FA)The FA is the tunnel end-point and forwards packets to the MN.Many MN using the FA can share this COA.

Co-located COAMN temporarily acquired an additional IP address which acts as COA.Tunnel end-point is at the MN.Co-located care-of address can be acquired using services such as DHCP



Example network

mobile end-systemInternet

router

router

router

end-system

FA

HA

MN

home network

foreign network

(physical home networkfor the MN)

(current physical network for the MN)

CN



Data transfer to the mobile system

Internet

sender

FA

HA

MN

home network

foreignnetwork

receiver

1

2

3

1. Sender sends to the IP address of MN,HA intercepts packet (proxy ARP)

2. HA tunnels packet to COA, here FA, by encapsulation

3. FA forwards the packet to the MN

CN



Data transfer from the mobile system

Internet

receiver

FA

HA

MN

home network

foreignnetwork

sender

1

1. Sender sends to the IP addressof the receiver as usual,FA works as default router

CN



Overview

CN

routerHA

routerFA

Internet

router

1.

2.

3.

homenetwork

MN

foreignnetwork

4.

CN

routerHA

routerFA

Internet

router

homenetwork

MN

foreignnetwork

COA



Mobile IP Design GoalsA mobile node must be able to communicate with other nodes afterchanging it’s link-layer attachment, yet without changing its IP address

A mobile node must be able to communicate with other nodes that do not implement mobile IP

Mobile IP must use authentication to offer security against redirectment attacks

The number of administrative messages should be small to save bandwidth & power

Mobile IP must impose no additional constraints on the assignment of IP addresses



Protocol OverviewAdvertisement

HA and FA periodically send advertisement messages into their physical subnetsMN listens to these messages and detects, if it is in the home or a foreign network MN reads a COA from the FA advertisement messagesA mobile node can solicit for mobility agents

Registration - when a mobile node is away from home, it must register its care-of address with it’s home agent

these actions have to be secured by authentication

Delivering DatagramsDatagrams must be forwarded by the Home Agent to the Foreign Agent for delivery to the care-of address.The delivery mechanism must handle all packets (including broadcast and multicast)A tunnel is used for this



Overall Behaviors



1. Agent DiscoveryProblems:

How to find a foreign agent?How does the MN discover that it has moved?Agent advertisement and Agent solicitation

Agent advertisementHA and FA advertise their presence periodically using Agent advertisement messagesICMP (Internet Control Message Protocol) message with some mobility extensions : RFC 1256

IP header: TTL=1destination IP: 224.0.0.1 (multicasting), 255.255.255.255(broadcasting)



type = 16length = 6 + 4 * #COAsLifetime: max lifetime in seconds

a node can requestR: registration requiredB: busy, no more registrationsH: home agentF: foreign agentM: minimal encapsulationG: GRE encapsulationr: =0, ignored (former Van Jacobson compression)T: FA supports reverse tunnelingreserved: =0, ignored

Agent advertisement

preference level 1router address 1

#addressesType=9

addr. size lifetimechecksum

COA 1COA 2

type = 16 sequence numberlength

0 7 8 15 16 312423Code

preference level 2router address 2

. . .

registration lifetime

. . .

R B H F M G r reservedT



Agent SolicitationMN can send Agent solicitation message

If no agent advertisement are present, The inter-arrival time of agent advertisements is too high, orThe MN just power on.Based on RFC 1256, ICMP router solicitation message

Move detectionMove detection using lifetime

If a MN fails to hear an advertisement from the foreign agent (or home agent) with the specified Lifetime.The MN can assume that it has moved to a different link, waits Agent Advertisement or sends Agent Solicitation.

Move detection using network-prefixesIf the network-prefix of the received Agent Advertisement is different from thethat of the previous foreign agent, then registration process should be invoked.



2. RegistrationRequest forwarding services when visiting a foreign network

This allocates a local (foreign) node address

Inform home agent of their current care-of addressThis creates a binding of the foreign node address to the home address

Renew a binding that’s about to expireBindings have lifetimes

De-register when they return home



Registration and SecurityThe home node and the mobile node have conducted some form of prior key exchange

This defines a “secret” between the two nodesThe authentication mechanism must defend against replay attacks

A replay attack occurs when a 3rd party can capture your packets and then “replay” them, fooling you into thinking they are correctly authenticated.

E.g., sending an encrypted password over a network leaves you open to a replay attack. Note that attack didn’t decrypt.Nonces: Each message from A -> B includes a new random number. When B replies to A, it must include that same random number. Likewise, each B->A message includes a new random number generated by B and echoed by A.



Registration RequestRegistration Request Message

The message is sent to FA when foreign agent care-of address is used or R bit of Advertisement is set.The message is directly sent to HA when collocated care-of address is used .

t

MN FA HAregistrationrequestregistrationrequest

registration

reply

registration

reply t

MN HAregistrationrequest

registration

reply



Registration Request

•Both send to UDP

port 434. (Registration Reply also)

• IP source address: interface address of the MN

• IP destination address:

•HA: when co-located care-of address is used•FA: when FA care-of address is used



Registration RequestType =1S – set to 1 to ask that its HA create or delete a binding for the specified care-of address.B – to tell the HA to encapsulate broadcast datagrams from home network to the care-of address.D – to inform the HA where the exit-point of the tunnel is located.Lifetime – the number of seconds it would like its registration to last before it expires.Home addressHome agent addressCare-of addressIdentification – 64 bits for replay protection.Mobile-home authentication extension – to prevent remote redirect attack.



Registration Request



Registration ReplyLifetime:tells the mobile node how long the registration will be honored by the HA.

It can be shorter than requested, but never longer.

registration successful0 registration accepted1 registration accepted, but simultaneous mobility bindings unsupported

registration denied by FA65 administratively prohibited66 insufficient resources67 mobile node failed authentication68 home agent failed authentication69 requested Lifetime too long

registration denied by HA129 administratively prohibited131 mobile node failed authentication133 registration Identification mismatch135 too many simultaneous mobility bindings



3. TunnelingTunnel

Establishes a virtual pipe for data packets between a tunnel entry and a tunnel endpoint.Tunneling is achieved by using encapsulation



Encapsulation

original IP header original data

new datanew IP header

outer header inner header original data

Encapsulation Mechanism of taking a packet consisting of packet header and data and putting it into the data part of a new packet.Decapsulation: reverse operationOuterheader: the new headerIP-in-IP-encapsulation, minimal encapsulation or GRE (Generic Record Encapsulation)



Encapsulation (IP-in-IP)IP-in-IP-encapsulation (mandatory, RFC 2003)

tunnel between HA and COA

Care-of address COAIP address of HA

TTLIP identification

IP-in-IP IP checksumflags fragment offset

lengthDS (TOS)ver. IHL

IP address of MNIP address of CN


lay. 4 prot. IP checksumflags fragment offset


TCP/UDP/ ... payload



Encapsulation (IP-in-IP)The outer IP header source & destination address identify the tunnel endpoints (e.g., HA & FA).Outer protocol is ‘4’ (IP protocol)

Indicates payload is also IP datagram (version 4)

The inner IP header source address and destination address identify the original sender & recipient

Not changed by the encapsulator, except to change TTLTTL is changed to 1 (why?)

Other headers for authentication might be added to outer header.Some outer IP header fields are copied from the inner IP fields (TOS), most are re-computed (TTL, checksum, length) based on new datagram



Encapsulation (Minimal)Minimal encapsulation (optional)

avoids repetition of identical fieldse.g. TTL, IHL, version, DS (RFC 2474, old: TOS)only applicable for unfragmented packets, no space left for fragment identification

care-of address COAIP address of HA


min. encap. IP checksumflags fragment offset


IP address of MNoriginal sender IP address (if S=1)

Slay. 4 protoc. IP checksum


reserved



Generic Routing Encapsulationoriginalheader

original data

new datanew header

outer headerGRE

headeroriginal data

originalheader

Care-of address COAIP address of HA


GRE IP checksumflags fragment offset


IP address of MNIP address of CN


lay. 4 prot. IP checksumflags fragment offset



routing (optional)sequence number (optional)

key (optional)offset (optional)checksum (optional)

protocolrec. rsv. ver.CRK S s

RFC 1701

RFC 2784

reserved1 (=0)checksum (optional)protocolreserved0 ver.C



Optimization of packet forwardingTriangular Routing

sender sends all packets via HA to MNhigher latency and network load

“Solutions”sender learns the current location of MNdirect tunneling to this locationHA informs a sender about the location of MNbig security problems!

Change of FApackets on-the-fly during the change can be lostnew FA informs old FA to avoid packet loss, old FA now forwards remaining packets to new FAthis information also enables the old FA to release resources for the MN

HA FA

NodeSource

HA FA

NodeSource



Change of foreign agent CN HA FAold FAnew MN

MN changeslocation

t

Data Data DataUpdate

ACK

Data Data

RegistrationUpdate

ACKData

Data DataWarning

Request

Update

ACK

DataData

Registration to HA is not shown

Smooth Handover



Reverse tunneling

Internet

receiver

FA

HA

MN

home network

foreignnetwork

sender

3

2

1

1. MN sends to FA2. FA tunnels packets to HA

by encapsulation3. HA forwards the packet to the

receiver (standard case)

CN



Mobile IP with reverse tunnelingRouter accept often only “topological correct“ addresses (firewall!)

a packet from the MN encapsulated by the FA is now topological correctfurthermore multicast and TTL problems solved (TTL in the home network correct, but MN is to far away from the receiver)

Reverse tunneling does not solveproblems with firewalls, the reverse tunnel can be abused to circumvent security mechanisms (tunnel hijacking)optimization of data paths, i.e. packets will be forwarded through the tunnel via the HA to a sender (double triangular routing)

The standard is backwards compatiblethe extensions can be implemented easily and cooperate with current implementations without these extensions Agent Advertisements can carry requests for reverse tunneling



Soft Tunnel StateRelaying ICMP (Internet Control Message Protocol) [RFC 792] Messages

HA FA MN1

Source1

tunnel

Source2

MN2ICMP error message

???ICMP message is sent to the tunnel entry-point (HA).How to relay the message and to whom?



Soft Tunnel StateTunnel entry-point necessary to relay certain ICMP messages to the original source.HA maintains soft state per each tunnel.

Path MTU The number of hopsWhether or not the end of tunnel is reachable.

HA updates its soft state based upon ICMP messages received fromrouters within the tunnel.

If the received ICMP message is “fragmentation needed”, then increase path MTU.If HA receives the ICMP “time exceeded”, then increase the length of the tunnel.If HA receives “destination unreachable”, then it knows that the tunnel is now un reachable.



Soft Tunnel StateWhen HA receives a IP datagram, check the soft state of the tunnel that will be used.

If the tunnel has a problem, then Send a ICMP message to the source without sending the datagram to the destination.

Why do we call the information as “soft state”?



Proxy and Gratuitous ARPHosts remaining on the home network sends IP packets to the linkwith MN’s MAC address that is stored in ARP cache.

So, HA must perform proxy ARP for the mobile node.

HA

S MNARP cache

MN

MAC frame



Proxy and Gratuitous ARPHA broadcasts gratuitous ARPs to the hosts on the link as soon as the MN moves away form the home network

Every node updates its ARP cache.IP home address of the MN ↔ MAC address of the HA

When MN returns to the home network, HA broadcast gratuitous ARPsIP home address of the MN ↔ MAC address of the MN

HA

S MNARP cache

1. ARP

2. to HA



Mobile IP and IPv6Mobile IP was developed for IPv4, but IPv6 simplifies the protocols

security is integrated and not an add-on, authentication of registration is includedCOA can be assigned via auto-configuration (DHCPv6 is one candidate), every node has address autoconfigurationno need for a separate FA, all routers perform router advertisement which can be used instead of the special agent advertisement; addresses are always co-locatedMN can signal a sender directly the COA, sending via HA not needed in this case (automatic path optimization)“soft“ hand-over, i.e. without packet loss, between two subnets is supported

MN sends the new COA to its old routerthe old router encapsulates all incoming packets for the MN and forwards them to the new COAauthentication is always granted



Problems with mobile IPSecurity

authentication with FA problematic, for the FA typically belongs to another organization no protocol for key management and key distribution has been standardized in the Internet

Firewallstypically mobile IP cannot be used together with firewalls, special set-ups are needed (such as reverse tunneling)

QoSmany new reservations in case of RSVPtunneling makes it hard to give a flow of packets a special treatment needed for the QoS

Security, firewalls, QoS etc. are topics of current research anddiscussions!



IP version 6 (Mobile IP)

notification of home agent and other correspondents

Collocated care-of address

registration with home agent

Router DiscoveryAgent Discovery

Care-of address obtained via Stateless Address autoconfiguration, DHCP, or

manually

Care-of address obtained via Agent Discovery,DHCP, or manually

All care-of addresses are collocatedForeign agent care-of address

A “plain” IPv6 router on the foreign link(foreign agent no longer exists)

Foreign agent

Globally routable home address and link-local home address

Mobile node’s home address

(same)Mobile node, home agent, home link, foreign link

Mobile IPv6Mobile IPv4



4. IP Micro-mobility support

Limitation of traditional Mobile IP

Mobile IP can result in disruption to user traffic during handoff.Mobile IP has high control overhead due to frequent notification to the HA.On every handoff, new QoS reservation would be reestablished from the HA to the FA even though most of the path remains unchanged.Thus,Mobile IP has some limitation when applied to wide-area wireless networks with high mobility users that may require QoS.



IP Micro-mobility supportMicro-mobility support:

Efficient local handover inside a foreign domain without involving a home agentReduces control traffic on backboneEspecially needed in case of route optimization

Example approaches:Cellular IPHAWAIIHierarchical Mobile IP (HMIP)

Important criteria:Security Efficiency, Scalability, Transparency, Manageability



Mobility ClassificationMicro-mobility is the movement of an MN within or across different BSs within a subnet and occurs very rapidly. (local mobility)

Macro-mobility is the movement of an MN across different subnet within a single domain or region,and occurs relatively less frequently. (intradomain mobility)

Global Mobility is the movement of an MN among different administrative domains or geographical regions. (interdomain mobility)



Cellular IPOperation:

“CIP Nodes“ maintain routing entries (soft state) for MNsMultiple entries possibleRouting entries updated based on packets sent by MN

CIP Gateway:Mobile IP tunnel endpointInitial registration processing

CIP Gateway

Internet

BS

MN1

data/controlpackets

from MN 1

Mobile IP

BSBS

MN2

packets fromMN2 to MN 1



Cellular IP(Routing)Cellular IP gateway periodically broadcasts a beacon packet that is flooded in the access network.

Base station records the neighbor they last received this beaconfrom and use it to route packets toward gateway.

All packets transmitted by mobile hosts, regardless of their destination address, are routed toward the gateway using these routes.



Cellular IP(Routing)

As these packets pass each node en route to the gateway,their route information is recorded as followsEach base station maintains a routing cache.Soft state mapping remains valid for a system-specific time called route-time-out.As long as mobile host X regularly sends data packet,base station along the path between Gateway and Mobile Host XTo keep its routing cache mappings valid,the mobile host transmit route-update packets on the uplink at regular intervals called route- updated time

Gateway, care of address

BS1(X,BS2)

BS2 (X,BS3)

BS3

Mobile Host X

Data packet are transmitted by MH

Data packet are destined to MH X

Beacon packet

R

R(X,BS1)



Cellular IP(Handoff)Cellular IP hard handoff is based on a simple approach that trade off some packet loss for minimizing handoff signaling rather than try to guarantee zero packet loss.

Cellular IP semisoft handoff exploits the notion that some mobile hosts can simultaneously receive packets from the new and old base stations during handoff.

Semisoft handoff minimizes packet loss,providing improved TCP and UDP performance over hard handoff.



Cellular IP(Hard Handoff)

To perform handoff,a mobile host tunes its radio to a new base station and sends route-update packet.

In the case of hard handoff handoff latency is equal to the round-trip time between mobile host and crossover BS. (In the worst case the crossover BS is the gateway.



Cellular IP(Semisoft Handoff)Semi-soft handoff scales well for large number of mobile hosts and frequent handoff.Semi-soft handoff comprises two architectural components.

In order to reduce handoff latency,the routing cache mappings associated with the new base station must be created before the actual handoff takes place.In order to resolve unsynchronized packet,mapping created at crossover points by the reception of semisoft packets include a flag to indicate that downlink packets must pass through a delay device before being forwarded for transmission along the new path.



HAWAIIHandoff-Aware Wireless Access Internet InfrastructureOperation:

MN obtains co-located COAand registers with HAHandover: MN keeps COA,new BS answers Reg. Requestand updates routersMN views BS as foreign agent

Security provisions:MN-FA authentication mandatoryChallenge/Response Extensions mandatory

BS

12

3

BackboneRouter

Internet

BS

MN

BS

MN

CrossoverRouter

DHCPServer

HA

DHCP

Mobile IP

Mobile IP

1

24

34



Hierarchical Mobile IPv6 (HMIPv6)Operation:

Network contains mobility anchor point (MAP)

mapping of regional COA (RCOA) to link COA (LCOA)

Upon handover, MN informsMAP only

gets new LCOA, keeps RCOAHA is only contacted if MAPchanges

MAP

Internet

AR

MN

AR

MN

HA

bindingupdate

RCOA

LCOAoldLCOAnew



5. DHCP: Dynamic Host Configuration Protocol

ApplicationIf a new computer is connected to a network, DHCP provide it with all necessary information for full system integration into the network.supplies systems with all necessary information, such as IP address, DNS server address, domain name, subnet mask, default router etc.enables automatic integration of systems into an Intranet or the Internet, can be used to acquire a COA for Mobile IP

Client/Server-Modelthe client sends via a MAC broadcast a request to the DHCP server: DHCP Discover.

client relay

clientserver

DHCPDISCOVER

DHCPDISCOVER



DHCP - protocol mechanisms

time

server(not selected)

client server(selected)initialization

collection of replies

selection of configuration

initialization completed

release

confirmation ofconfiguration

delete context

determine theconfiguration

DHCPDISCOVER

DHCPOFFER

DHCPREQUEST(reject)

DHCPACK

DHCPRELEASE

DHCPDISCOVER

DHCPOFFER

DHCPREQUEST(options)

determine theconfiguration

List of configuration parameters



DHCP characteristicsServer

several servers can be configured for DHCP, coordination not yetstandardized (i.e., manual configuration)

Renewal of configurationsIP addresses have to be requested periodically, simplified protocol

Optionsavailable for routers, subnet mask, NTP (network time protocol) timeserver, SLP (service location protocol) directory, DNS (domain name system)

Big security problems!no authentication of DHCP information specified



6. Mobile IP multicasting problem definition

IETF Standards

Remote-subscription Optimal routing (con)Frequent multicasting tree updating (pro)Join delay (pro)Out-of-synch problem (pro)

Bidirectional-tunnelingNo out-of-synch problem (con)No tree updating and join procedure (con)Multiple unicast tunnels from a HA to a FA (pro)Multiple tunnels from different HAs to a FA (pro)No optimal routing (pro)Registration delay

Internetwork

Mobile Host Mobile Host

Correspond Node

FA(HA) FA

Move

Membership Add

Internetwork

Mobile Host Mobile Host

Correspond Node

FA(HA) FA

Move



Mobile IP MulticastingMOM (ACM Mobicom’97)

Use bidirectional tunnelingSolve tunneling convergence problemSelect one HA from multiple HAs in FA for a group: DMSP

HA

FA

HAHA HA

FA

HAHA

DMSP



DMSP selection methodsAge-based, count-based

DMSP handoff eventsMHs of DMSP movementNew MH comes in

Problems of MOMNo optimal routing (still exists)Out-of-synch problem (newly generated)Registration delay for tunneling (still exists)Losses during DMSP handoff (newly generated)



RBMOM (IEICE Trans. on Comm. 2001)Hybrid: bidirectional tunneling & remote subscriptionMethod

D=distance between FA and MHADh=distance between FA and HAMHA: multicast agent for a MH (HA or FA)R=predetermined threshold distance (hop count)

When a MH moves to a new FAIf (D > R)

if (Dh<=R)if(FA is on the multicast tree)

MHA=FAelse MHA=HA

elseMHA=FAif FA is not on the tree, then join the treeinform to HA that FA is now MHA for the MHinform to the previous MHA that it does not need to send data.

Elseinform to the MHA the location of the new FA(RBMOM can use DMSP approach on selecting MHA)



Problems of RBMOMIt does not consider reliable multicastingData structure and operational procedures for all agent types are not perfect.Distance between FA and MHA is not only thing to decide for joining the tree.HA is receiving the multicasting data (as a member of the tree) even though there is no MH that is receiving data from the HA.

RBMOM modification (IEE Electronics Letters, 2002)Service range R (distance from MHA to the new FA) is dynamicallydecided by MHA

So, tunneling or joining the tree is decided by MHA not FAR*(1hop delay)+TDs-mha+Ttunnel<=maxDelayTDs-mha=(hops from S to MHA)*(1hop delay)Ttunnel= tunneling process delay



MMROP (IEEE Trans. on Consumer Electronics, 2001)Basically, use IETF-RS methodTo solve out-of-synch problem, missing sequence packets are transmitted by tunnel between new FA and old FA.

ProblemsIt still has many problems of RS

FA FA FA

join

S

1) 7.8.9

1.2.3

2) leave[4,6]

3) 4.5.6



REMMIPObjectives

Tunneling from MA (multicast agent, HA or FA) instead of HA.FA can be a MA for the MH that visited before.Reduce path length from source to MH.Reduce packet loss and out-of-synch problem

Eliminate HAs from multicasting treeIf it does not have any MHs in its home network and it does not act as MA for other FAs.

Reliable and efficient mobile IP multicasting mechanism.

MAHA maintains the MH’s location.MA is the agent that has a responsibility to send multicast data to a certain FA.MA should join the multicast tree.



1. MH moves to new FAMH sends the GroupInfo when it initiates normal mobile IP registration procedure.IF the new FA does not receives data of the group.

The MH is the first host of the group.FA sends TUNNELING REQUEST[SEQmh+1] to the MA of the MHFA sets the MH’s MA to the FA’s MAIF there is out-of-synch problem, FA requests RECOVERY REQUEST [SEQmh+1, SEQma-1] to the MH’s prev agent. Optionally, MH can send MOVE message to the MH’s prev agent.

HA

FA

1. TR[SEQmh+1]2. Data transmission3. RR[a,b]4. Recovery data

MARegistration(GroupInfo)

Normal MIP registration

FA

S

1

2 34

Sequence Number

SEQmh

MA Address

HA Address

Prev Agent Address

Group ID

GroupInfo



IF the new FA has already received data from other MA.FA selects a MA from the possible MA candidates (current and new).

MA changes cause out-of-synch problem for the existing MHs, so it is not recommended.MA selection events

• When a new MA candidate is added.

Many MA selection methods can be considered.

IF the MA of the FA is not changed.Notify (MA CHANGE) to the new MH.IF FA cannot send all data [SEQmh+1,SEQfa] to the new MH, FA requests RR [SEQmh+1, SEQfalast-1] to the MH’s prev Agent.

• After FA received the data, it forwards them to the new MH.

Optionally, the new MH can send MOVE message to the MH’s prev agent.



IF FA selects a new MA(MH’s MA).Notify (MA CHANGE) to all MHs except the new MH in FA network that MA has been changed.FA sets the new MA as its MA.IF FA cannot send all data [SEQmh+1,SEQfa] to the new MH, FA requests RR [SEQmh+1, SEQfalast-1] to the MH’s prev Agent.

• After FA received the data, it forwards them to the new MH.

FA sends TUNNELING REQUEST[SEQfa+1] to the new MA.IF there is out-of-synch problem, FA sends RR[SEQfa+1, SEQma-1] to the FA’s prev MA. FA sends STOP to the FA’s prev MA.FA sends reordered data to all MHs in the network..Optionally, the new MH can send MOVE message to the MH’s prev agent.

FA

MA

FA

S

MAnewprev

prev

1. MC

SEQmh

SEQfa

2. RR

3. data4

5.TR6.data

7.RR

8.data

9.STOP



2. BT to RS by FAWhen FA is not on the tree and uses BT, if one of the following conditions is satisfied, then join the multicasting tree.

1) #MH > Th(N)If the number of MHs is greater than threshold value – many customers: optimal routing

2) min(MHt)>Th(T)If the minimum staying time of MHs is greater than threshold value – slow mobility

3) Hop(DMSP-FA)>Th(H) If the number of hops from DMSP to FA is greater than threshold value – reduce hop count

MA

FA

S

2) Join

1)1.2.33) 7.8.9

6) STOP[4,6]

7) 4.5.6

8) 4.5.6.7.8.9

4) MA=FA

5) MA CHANGE(MA=FA)



3. IF agent(HA, FA) recognizes MH’s leaving.All agents can know MH’s leaving

Soft state: MH and/or agent periodically transmits membership message.Explicit MOVE message is sent by MH.

IF there exists no MH of a multicast group.TEHNCase 1: MA of the agent = Agent (the agent joined tree)

Check there is any FA that is served by the agent.IF no, wait a moment (because of RECOVERY REQUEST)

Leave from the multicast tree.

FA

or HA

All hosts moved.

FAFASTOP STOP

SPRUNE



Case 2: MA of the agent! =Agent (the agent is served by other agent) Wait a moment (because of RECOVERY REQUEST)Send STOP to the agent’s MA to finish tunneling.

FA

or HA

All hosts moved.

MASTOP

S

MH Lists

Served FA Lists

SEQ(agent)

Prev MA Address

Group ID

MA Address

Group ID

Only if the agent joined the tree

If the agent joined the tree,then MA=Agent address

MHs that are in the agent network

Documents

Mobile Computing Chapter 8: Mobile Network Layermultinet.ivyro.net/recruit/lecture/1-2/mbc-8.pdf · 2008. 10. 7. · Mobile IP Design Goals A mobile node must be able to communicate